One method of fabricating machines and other articles from metal involves the torch-cutting of components from metal plate. Although this method is reasonably efficient, the component produced in this manner is surrounded at its edges by rough ridges of slag which must be removed to restore the surface flatness and appearance of the component prior to further assembly.
Slag removal is conventionally accomplished by unskilled workers using chipping hammers or hand grinders. An improvement on this manual approach is the slag grinding machine, in which a horizontal conveyor moves the workpieces relative to a grinding head. The grinding head consists of a wide, endless abrasive belt driven around upper and lower rollers, the lower of which is disposed in overlying relation to the conveyor with its axis of rotation substantially perpendicular to the line of conveyor movement. The abrasive belt, in passing around the lower roller, defines a line or region of abrasive contact with the workpieces as they pass between the abrasive belt and conveyor. The space between the belt and conveyor is adjusted based on the thickness of the workpiece.
The abrasive belt is necessarily moved against the direction of conveyor movement to effect slag removal, since abrasive belt movement in the same direction as the conveyor would simply result in projecting the workpieces forward at high speed with little or no grinding. Because of this direction of abrasive belt movement, it is also necessary to employ transversely disposed, driven pinch rollers disposed in overlying relation to the conveyor belt and upstream of the grinding head to insure that the workpieces are continuously and uniformly fed to the abrasive belt.
The slag grinding machines of this type are highly efficient relative to the manual approach of slag removal and represent a considerable saving of labor time and cost in prevention. However, because there is a practical limitation on the closeness of the pinch rollers to the grinding head, there is also a lower limit to the size of workpieces that can be efficiently handled. If the workpiece has a smaller dimension than the distance between the pinch rollers and grinding head, it will not be driven through the grinding area; and, since the abrasive belt moves in a direction against conveyor movement, the small workpiece can become stalled between the two, unable to move forward. This may result in jamming of the machine since following workpieces may likewise be unable to proceed forward.